R.sup.6 may represent e.g. an acetyl or benzoyl group.
The frequency of occurrence of allergic diseases, particularly bronchial asthma is continuously increasing. Social-economical and environmental conditions, enhancement of effectivity of the diagnostics and the lack of an adequate, really healing therapy provide background for this increase. Despite of or partially even due to the elevated drug consumption, the mortality ratio also shows a rising tendency.
Asthma is characterized by an increased sensitivity of the respiratory smooth muscles to the most various stimuli, which leads to a reversible constriction or obstruction of the airways. Chronic asthma eventually results in an irreversible airway obstruction.
Here, an uncontrolled inflammatory process of the respiratory tract appears to be involved. A therapy, which is based only on a bronchodilatation without affecting and even masking the above process represents a merely symptomatic treatment which is essentially harmful and likely contributes to the increase in the mortality.
In opposition to this, an antiinflammatory therapy suppresses the inflammation and at least slows down the harmful background process as well as diminishes the frequency of the demand on a simultaneously used bronchodilatory treatment.
In the cases of drugs being available at present, a further problem appears in the adverse effects decreasing to a high degree their usefulness.
Thus, a most advantageous therapy could be ensured by a drug which is effective against mediator substances causing a spasm of the respiratory smooth muscles and simultaneously possessing antiinflammatory or antiallergic effect without any adverse side effect.
Due to the pathologic nature of bronchial asthma, the effects against the possibly highest number of mediator substances, being constrictive or even inflammatory in character, is very important since the actions of many kinds of endogeneous substances are simultaneously exerted. It would be arbitrary to suppose an outstanding role of any component. Thus, the simultaneous presence of each of the effects defined above is important for these drugs to be developed for the treatment of bronchial asthma.